Devices housed in cavities of the interconnection parts (BEOL) of integrated circuits and having at least one mobile metal piece are known. They may, for example, form switches which are used to establish or interrupt electrical connections, or alternatively may form capacitors having thermally variable capacitive values.
Such devices are described, for example, in published Patent Applications FR 2984009, FR 2984010, and WO 2013/083385. These foreign applications correspond to U.S. Pat. No. 8,884,289, U.S. Pat. No. 8,704,327, and U.S. Patent Appl. Pub. No. 2014/0266562.
Although these devices are entirely satisfactory, in certain cases it may occur that the metal pieces mobile relative to one another become oxidized at the surface in contact with the air present in the cavity.
The result of this, when the device is used as a switch, is then a reduction in the quality of the ohmic contact between these metal pieces, which may in the worst case lead to the establishment of an electrical connection passing through these metal parts being prevented.
When the device is used in order to form a capacitor with a variable capacitive value, the formation of a metal oxide on the surface of these pieces next to one another may create an additional dielectric, which will modify the expected value of the capacitive value of the capacitor for a given distance between these metal pieces.
One embodiment proposes to avoid as far as possible the degradation of an ohmic contact or the formation of an additional dielectric at pieces, mobile relative to one another, of a device accommodated in a cavity, and to do so while remaining compatible with CMOS technologies and with a reduced extra volume cost.